Absorption refrigeration



Jan. 24, W67 R. H. MERRECK ABSORPTION REFRIGERATION Filed July 26, 19652 Sheets-Sheet 1 INVENTQR.

RICHARD H. MERRICK.

ATTQRNEY.

Jan. 24, 3967 R. H. MERRICK 3,299,669

ABSORPTION REFRIGERATION Filed July 26, 1965 2 Sheets-Sheet Z qpg.

, I I i I l 1 l J ATTORNEY.

United States Patent M 3,299,669 ABSORPTION REFRIGERATION Richard H.Merrick, Indianapolis, Ind., assignor to Carrier Corporation, Syracuse,N.Y., a corporation of Delaware Filed July 26, 1965, Ser. No. 474,834 13Claims. (Cl. 62-476) This invention relates to absorption refrigerationand more particularly to absorption refrigeration machines havingrefrigerant evaporators of the type which are adapted to cool air.

This invention will be described with reference to the preferredembodiment thereof wherein it is employed in conjunction with anabsorption refrigeration system of the type using ammonia as arefrigerant and water as an absorbent. Because of the desirabletemperaturepressure characteristics of such systems, it is commonpractice to use an ammonia-water system for air cooled absorptionrefrigeration machines.

Since ammonia vapor is toxic, it is necessary to assure that the ammoniarefrigerant does not leak into the air being cooled during operation ofthe refrigeration machine. It has therefore been standard practice toprovide a secondary chilled water circuit in conjunction with ammoniaabsorption machines. In such prior systems, the ammonia is evaporated inan evaporator coil to cool water which is passed thereover. The water isthen pumped by means of :a chilled water pump to a secondary heatexchanger in a desired remote location. Air is passed over the secondaryheat exchanger and is cooled by heat exchange with the chilled water.The chilled water is then returned through return conduits back to theevaporator where it is re-chilled by passing in heat exchange relationwith the refrigerant in the evaporator coil. Should a leak occur in theevaporator coil due to corrosion or other damage, the ammonia will passinto the chilled water circuit, but will not leak into the air beingcooled. The chilled water circuit is vented to the atmosphere so thatammonia leaking into it can escape to a location where it will not causeinjury to occupants of the conditioned space.

Prior systems of the type described require a secondary chilled waterpump, a secondary refrigerant heat exchanger :and secondary refrigerantpiping to connect the secondary heat exchanger to the evaporator coil.These components materially add to the cost of refrigeration systems ofthe type described. It would be desirable to achieve the safety of avented secondary chilled water system, but at the same time, toeliminate the cost and complexity of the secondary heat exchanger,secondary chilled water pump, and their associated piping.

It is a principal object of this invention to provide an improvedabsorption refrigeration system for cooling air which is adapted toemploy :a toxic refrigerant without danger of refrigerant leakage intothe air being cooled.

It is a furtherv object of this invention to provide an improvedrefrigeration system of a type having an evaporator which is adapted toemploy a toxic refrigerant without danger of refrigerant leakage intothe space being refrigerated.

In accordance with a preferred embodiment of this invention there isprovided an improved evaporator construction for an absorptionrefrigeration machine of the type employing amomnia as a refrigerant andwater as an absorbent. The evaporator may comprise a pair of tube sheetshaving a plurality of heat exchange tubes disposed therebetween for heatexchange with the air being cooled. Evaporator tubes are disposed withinthe heat exchange tubes and are connected between the condenser andabsorber of the absorption refrigeration Patented Jan. 24, 1967 machine.A suitable displaceable liquid medium such as water is disposed betweenthe evaporator tubes and the interior of the heat exchange tubes. Liquidfilled headers are disposed about the tube sheets so that the evaporatorcoil is submerged in the liquid medium. At least one of the headers isvented to the atmosphere or some other suitable location. Preferably, alayer of oil or other relatively non-volatile fluid may overlie thesurface of the liquid medium in the vented header to prevent loss of theliquid by evaporation, if the liquid medium is one which is readilyvolatilized in use.

The liquid medium is disposed in :a thin layer between the heat exchangetubes and the evaporator tubes. The thin layer of liquid providedrelatively good heat conduction between the evaporator tubes and theheat exchange tubes. At the same time, the liquid medium is displaceableand serves as a path for the escape of refrigerant in the event that adefect should occur in the wall of the evaporator tubes of a naturewhich permits refrigerant to escape through the wall of the evaporatortubes. In that event, the escaping refrigerant will pass through theliquid medium between the evaporator and heat exchange tubes, andthrough the tube headers to the atmosphere or other location to whichthey are vented. Thus, escape of refrigerant into the stream of airbeing cooled is prevented. Furthermore, the use of water as the liquidmedium surrounding the evaporator tubes and in the headers has theadditional advantage of serving as an absorbent medium to absorbescaping refrigerant. The liquid medium surrounding the evaporator tubesmay also contain a suitable corrosion inhibitor to reduce the likelihoodof failure of evaporator tubes and to help prevent leakage ofrefrigerant.

The evaporator of the absorption refrigeration machine may be located sothat the headers are in heat exchange relation with ambient atmosphereto prevent evaporation of the liquid medium during the heating seasonand to prevent excessive condensation of moisture from the air into theheaders during the cooling season. The evaporator may be located in ahousing containing the other components of the absorption refrigerationmachine. However, the improved evaporator construction may be disposedinstead within an air duct in the interior of the building beingconditioned and the refrigerant liquid and vapor conduits extendingbetween the evaporator and an externally located absorptionrefrigeration machine, may be shrouded by a conduit which is vented tothe atmosphere.

These and other objects of this invention will become more readilyapparent by reference to the following specification and attacheddrawings wherein: '1 A FIGURE 1 is a schematic diagram partly in crosssection illustrating an obsorption refrigeration machine embodying oneapplication of this invention; and

FIGURE 2 is a perspective view partly in cross section illustrating 'aslightly modified application of this invention.

Referring particularly to the drawing, there is shown an absorptionrefrigeration system having an absorber 10, a

condenser 11, an evaporator 12, and a generator 13 connected to providerefrigeration. A pump 14 is employed to circulate weak absorbentsolution from absorber 10 to generator 13. As used herein, the term weakabsorbent solution refers to a solution which is weak in absorbingpower, and the term strong absorbent solution refers to a solution whichis strong in absorbing powder. A suitable absorbent solution for use inthe system described is water, and a suitable refrigerant is ammonia.For convenience, the absorbent liquid will be referred to as anabsorbent solution although it will be appreciated that pure water isnot technically a solution.

Liquid refrigerant is passed from condenser 11 through liquid line 23,refrigerant restriction 24, the exterior passage of liquid suction heatexchanger .25, second rcfrigerant restriction 26, and refrigerant line19 to evaporator tubes or coil 27 of evaporator 12. Heat from the air orother fluid to be chilled, passing over the evaporator, is given up tothe refrigerant which vaporizes in the interior passage of theevaporator. The refrigerant vapor passes from tubes or coil 27 throughvapor line 28, the interior passage of liquid suction heat exchanger 25,to mixing line 29 where it is mixed with strong solution returning tothe absorber from the generator.

The mixture of refrigerant vapor and strong solution passes throughmixing line 29 into the heat exchange tubes or coil which forms absorber10. Air is passed over the exterior of the absorber coil by fan 15 tocool absorbent solution therein and increase its absorbing power. Theabsorbent solution is weakened as it absorbs refrigerant vapor duringits passage through the absorber. By the time the absorbent solutionreaches the discharge end of the absorber coil, the refrigerant vapor iscompletely absorbed in the absorbent solution and the solution hasbecome weak in absorbing power by the absorption of the vapor.

The weak absorbent solution passes through weak solution line 30 to apurge tank 31 where noncondensible gases are collected and withdrawnfrom the system. The weak solution is then forwarded by solution pump 14through weak solution line 32 to combined rectifier and heat exchangersection 35.

Rectifier and heat exchanger section 35 comprises an outer shell 46forming a vapor passage. Shell 46 contains an inner heat exchange coil45 and a concentric outer heat exchange coil 36, as shown in thedrawing. Preferably outer heat exchange coil 36 is spirally disposedalong the inner wall of shell 46 and it may be provided with suitablefins for enhancing heat transfer.

Coils 36 and 45 form a solution heat exchanger between the entirequantity of relatively hot strong solution passing from the generator tothe absorber and the entire quantity of relatively cool Weak solutionpassing from the absorber to the generator. The amount of heat transfersurface provided between the strong and weak solution is designed sothat the weak solution is brought to just about its boiling point sothat vapor is not formed in the solution heat exchanger.

The weak solution from line 32 passes through coil 36 in the annularspace between inner heat exchange coil 45 and outer heat exchanger coil36 where the weak solution is heated to substantially its boiling pointby heat exchange with strong solution. After passing through coil 36,the heated weak solution is discharged from opening 37 onto one of aplurality of bafiles or plates 39 in analyzer column 38.

Analyzer 38 comprises a tubular member having a plurality of plates 39which provide surfaces for contact of vapor with the reflux and thesolution which wets the surfaces of the plates. The weak solution passessuccessively over the plurality of plates and is discharged from thebottom of the analyzer into a generator reservoir 40. Generatorreservoir 40 provides solution storage for part load operationconditions and allows for solution and refrigerant charging tolerance,and compensates for manufacturing variations in machine volume.

Weak solution from generator reservoir 40 passes through line 49 intogenerator coil 50. The solution in coil 50 is heated by suitable meanssuch as gas burner 51 causing the solution to boil thereby formingvapor. The vapor and hot solution is discharged from coil 50 intoseparation chamber 53, formed by a baffle or weir 52, where the vaporseparates from the remaining strong solution. Preferably, some of thesolution normally spills over the top of baffle 52 and is recirculatedthrough line 49 to generator coil 50. It will be understood that thesolution in separation chamber 53 has been concentrated by vaporizingrefrigerant therefrom in generator 13.

Vapor formed in generator 13 passes concurrently with strong solutionthrough the vapor passage 55 formed in the upper portion of genertaorreservoir 40, through analyzer 38 and through the vapor passage formedby shell 46 of rectifier 35 to condenser 11.

The concentrated or strong absorbent solution from separation region 53is at the relatively high generator pressure and passes through heatexchange coil 48 in generator reservoir 40, heat exchange coil 47 in theanalyzer column, and inner :heat exchange coil 45 in the rectifier. Thestrong solution then passes through line 60 and restriction 61 intomixing line 29 and absorber 10 on the relatively low pressure side ofthe system.

Heat from the strong solution passing through coil 48 boils the weaksolution in the generator reservoir to vaporize refrigerant therefrom.The heat exchange which takes place in the generator reservoir resultsin cooling the strong solution flowing through coil 48 so that it entersthe analyzer and rectifier respectively at the best temperature toachieve maximum efficiency with minimum heat trans fer surface.

A portion of coil 48 is submerged below the level of weak solution inreservoir 40 and another portion of the coil is disposed in the vaporpassage above the weak solution. The boiling of the weak solution causesthe portion of coil 48 which is disposed in vapor passage 55 to bewetted with solution. As the strong solution passes through coil 48, itbecomes progressively cooler. Vapor formed in the generator and in thereservoir passes through the vapor passage 55 and contacts the exposedand wetted portion of coil 48 in reservoir 40, and mass and heattransfer takes place with the weak solution boiling in the reservoir. Itwill be appreciated that ammonia vapor will be boiled from the weaksolution in the reservoir and that water vapor will be condensed fromthe vapor space into the weak solution in proportions resulting in anenrichment of the refrigerant content of the vapor passing through thereservoir. Also the condensation of water vapor into the weak solutionwill liberate additional heat which assists in vaporizing the solution.

Similarly, as the vapor passes from the reservoir upwardly throughanalyzer column 38, a mass and heat transfer takes place 'between theweak solution passing downwardly over plates 39 in the columns andfurther enriches the refrigerant content of the vapor.

The vapor then passes through rectifier 35 Where it is placed in heatexchange relation with the weak solution passing through coil 36. Theheat transfer which takes place in the rectifier results in condensingadditional water from the vapor which then leaves the rectifier in ahighly purified or enriched state.

The purified refrigerant vapor passes from rectifier 35 through line 58into the coil of condenser 11. Fan 15 passes air over condenser 11causing the refrigerant vapor to condense. The condensed refrigerantpasses through line 23 and restriction 24 into evaporator 12, aspreviously explained.

As the vapor passes through rectifier 35, the reflux or solution whichis condensed, flows by gravity to analyzer 38 and passes downwardlythrough the analyzer column along with weak solution discharged fromoutlet 37 of coil 36. This rectifier condensate is heated along withweak solution in the analyzer to produce additional vapor by heatexchange with strong solution passing through coil 47,

In accordance with the embodiment of this invention illustrated inFIGURE 1, evaporator 12 includes a pair of spaced tube sheets 71 and 72.disposed therein. A plurality of hollow, parallel, heat exchange tubes75, having open ends, are disposed between headers 71 and 72 and aresecured in fluid tight engagement therewith. The evaporator alsoincludes a plurality of hollow tubular parallel evaporator tubes 20disposed concentrically within heat exchange tubes 75. Return hends 76are provided at the ends of evaporator tubes 20 to form an evaporatorcoil. Helical or longitudinal fins or other spacing means (not shown)may be provided on the exterior of evaporator tubes 20 or on theinterior of heat exchange tubes 75, or on both tubes, if desired.Preferably, heat exchange tubes 75 are provided with exterior plate-fins 77 or other extended heat transfer means for contact with air tobe cooled.

A refrigerant liquid line 19 extends between restriction 26 and thefirst evaporator tube 20 of the evaporator coil. A refrigerant vaporline 28 extends from the last evaporator tube 20 of the evaporator coilto absorber 10.

Headers 73 and 74 are connected in fluid tight engagement with tubesheets 71 and 72 respectively, and enclose return bends 76 and the openends of heat exchange tubes 75. A liquid medium 82, such as water, fillsheaders 73 and 74 to level 82 which is above the uppermost one of heatexchange tubes 75. A layer of relatively lighter, less volatile, andimmiscible liquid 83, such as oil, overlies the surface of the liquid 82in theevent the liquid is one which is readly vaporized during operationof the system. The oil, or other liquid, inhibits evaporation of theheat exchange liquid medium from headers 73 and 74. Liquid 82 maycomprise any displaceable or fiowable medium such as slurries or gels,and may include powdered metal for enhanced thermal conductivity.

Headers 73 and 74 may have a small vapor space at the upper portionthereof. The upper portions of at least one of the headers is vented tothe atmosphere or other suitable location by vent passages 80 and 81respectively.

Evaporator 12 in the embodiment shown in FIGURE 1 may be disposed in ahousing (not shown) containing the other components of the absorptionrefrigeration machine and the housing may be located exteriorly of thebuilding or other space being conditioned. Suitable duct or passagemeans is provided to admit either room air or outside air into theregion about heat exchange tubes 75 and fins 77. This air is passed overthe heat exchange tubes 75 where it is cooled 'by heat exchange with therefrigerant evaporating inside evaporator tubes 20, The cooled air isthen passed through duct 78 into the building or other desired location.

In the event of leakage of refrigerant from the evaporator coil, such asmight be occasioned by corrosion of evaporator tubes 20, the leakingrefrigerant will displace the liquid and pass through the space betweenevaporator tubes 20 and heat exchange tubes 75 into one or the other ofheaders 73 and 74. The refrigerant vapor will then pass upwardly throughthe liquid medium in the header and through the layer of oil or othernon-volatile liquid into vent passages 80 or 81, from which it isexhausted into the atmosphere.

In the event of a refrigerant leakage from the evaporator tubes, due tocorrosion of the tubes, the leaking refrigerant will displace the liquidand p ass between evaporator tubes 20 and heat exchange tubes 75 andinto one or the other of headers 73 and 74. The refrigerant cannot leakinto the stream of air passing over heat exchange tubes 75 and thereforewill not contaminate the stream of air being cooled. Even if the heatexchange tubes and the evaporator tubes nearly touch each other, thethin film of liquid medium between them will provide 'a path ofrelatively low resistance to'the passage of leaking refrigerant vapor tothe atmosphere or other desired location.

I It is desirable that the film of liquid medium between the heatexchange tubes and the evaporator tubes be relatively'thin inorder toenhance the heattransfer through the liquid medium which serves as aliquid heat transfer medium. Because the heat exchange tubes and theevaporator tubes are not in tight engagement with each other, thelikelihood of a corrosion path through an evaporator tube also extendingits way through a heat exchange tube is negligible.

The liquid medium 82 between heat exchange tubes 75 and evaporator tubes20 may comprise an absorbent medium such as water to further lessen thelikelihood of passage of refrigerant into the air stream being cooled.Thus, ammonia vapor leaking into the water between the evaporator tubesand heat exchange tubes will be absorbed in the water and any portion ofthe ammonia which is not absorbed in the water will be exhausted intothe atmosphere or other desired location through vent 80. It ispreferred and convenient to provide a suitable corrosion inhibitor inthe liquid medium, to lessen the corrosion of both the evaporator tubesand the heat exchange tubes. For example, sodium chromate may besuitably employed as an inhibitor where water is the liquid medium. Itwill be seen that corrosion of either the evaporator tubes 20 or returnbends 76 will not result in contamination of the air being cooled by therefrigerant by the practice of this invention. Alternatively, an oilsuch as engine oil may be used as the liquid medium. Engine oil is asuitable and a desirable liquid medium because of its relatively lowvolatility and its high stability; also, it normally has corrosioninhibitors dissolved in it which prevent corrosion of the metal tubes.

In the above described embodiment of this invention, evaporator 12 islocated outside of the building being conditioned, and the cooled air issupplied to the building through duct 78. Preferably, headers 73 and 74are disposed in heat exchange relation with the ambient atmosphere. Bythis means, the heat exchange fluid in the headers is cooled when theambient air is cold to thereby inhibit evaporation of the heat exchangeliquid during the heatingseason. On the other hand, when the ambient airis warm, such as during the cooling season, the tendency of moisturefrom the air to condense in vent passages 81, due to heat exchange withthe cold evaporator, is reduced.

A modified embodiment of this invention is illustrated in FIGURE 2. Inthis embodiment most of the components of the absorption refrigerationmachine are located exteriorly of the conditioned space in a suitablehousing 90. Housing has a grill 91 for admitting ambient air, and a fangrill 92 for exhausting the ambient :air from the housing. Evaporator 12is connected by conduits 19 and 28 to the remainder of absorptionmachine in housing 90. Preferably conduits 19 and 28 are disposedadjacent and in heat exchange relation with each other to form a liquidsuction heat exchanger 125. Evaporator 12 is located inside the buildingor other space to be conditioned in the warm air duct connecting furnace93 with air distribution duct 78.

Suitable joint means and valves 111, 112 may be provided to connectlines 19 and 28 with evaporator 12 and with the other components of theabsorption refrigeration machine. Evaporator 12 in this embodiment issimilar to the evaporator previously described except that an additionalouter vent tube or passage 96 is provided about and spaced fromrefrigerant lines,19. and 28 to receive any refrigerant which mayleakfrom either lines 19 or 28. Vent passage 96 is secured, adjacentv oneend 98 thereof, in sealing relation with housing 70 ofevaporator '12.Vent passage 96 extends from evaporator 12 through wall 99 ofthebuildingor space being cooled tothe outside or to some other suitablelocation at which it is safe to vent refrigerant vapor. End 97 of ventpassage 96 is preferably open to the atmosphere. Consequently,refrigerant leaking from either lines .19 or 28 is vented to the outsideof the space being cooled and the refrigerant cannot contaminate theconditioned area.

Vent passages 80 and 81 extending from header 73 are connected to ventline 94 which may either extend directly through wall 99 or mayterminate in outer tube 96 as shown in the drawing. As in the precedingembodiment, any refrigerant leaking from the evaporator coil 27 passesthrough the liquid heat exchange medium disposed sponsor;

7 in the space between evaporator tubes 20 and heat exchange tubes 75into passages 80 and 81, from which the refrigerant vapor is exhaustedto the atmosphere so that the air being cooled is not contaminated.

Various modifications of this invention may be envisioned within thescope thereof. For example, evaporator 12 may be employed incommunication with any refrigeration system wherein it is desired toprevent the cooling medium from escaping and contaminating the cooledspace. Consequently, evaporator 12 is suitable for use withrefrigeration systems employing such toxic refrigerants as sulfurdioxide and menthol chloride. Furthermore, the evaporator may bedisposed in any desired location because the danger of contamination ofthe conditioned air is minimized. A lso, evaporator 12 may assume otherconfigurations such as a continuous concentric serpentine coil having avented, liquid filled, header on at least one end of the outer tubethereof. While water has been described as being a desirable liquidmedium with which to fill the space between the evaporator tubes and theheat exchange tubes, it will be appreciated that other media such asmineral oil or engine oil may be satisfactory for this purpose. In asimilar manner fluids other than air may be cooled by an evaporator ofthe type described.

It will be seen that by the use of this invention, the necessity ofsecondary chilled Water pump and a separate secondary refrigerant heatexchange coil is eliminated so that the cost and complexity of arefrigeration system employing this invention is reduced. Furthermore,the invention is effective to prevent contamination of the cooled spaceirrespective of the nature of the refrigerant employed and makes itpossible to employ toxic refrigerants with safety.

While preferred embodiments of this invention have been described forpurposes of illustration, it will 'be appreciated that the invention maybe otherwise embodied within the scope of the following claims.

I claim:

'1. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide cooling, saidevaporator comprising:

' (1) an evaporator passage including an evaporator tube connected toreceive liquid refrigerant from said condenser and to dischargevaporized refrigerant to said absorber;

(2) a heat exchange tube enclosing at least a portion of said evaporatortube;

(3) a liquid medium filling the region between said evaporator tube andsaid heat exchange tube; and

(4) a passage means for passing any refrigerant leaking from saidevaporator tube into said liquid medium to a desired location.

2. An a'bsonption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide cooling, saidevaporator comprising:

(1) an evaporator passage including an evaporator tube connected toreceive liquid refrigerant from said condenser and to dischargevaporized refrigerant to said absorber;

(2) a heat exchange tube enclosing at least a portion of said evaporatortube;

(3) an absorbent .liquid medium capable of ab:- sorbing refrigerantdisposed between said evaporator tube and said heat exchange tube; and

(4) passage means for passing any refrigerant leaking from saidevaporator tube into said liquid medium to a desired location.

3. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide cooling, saidevaporator comprising:

(1) an evaporator passage including an evaporator tube connected toreceive liquid refrigerant from said condenser and to dischargevaporized refrigerant to said absorber;

(2) a heat exchange tube enclosing at least a portion of said evaporatortube;

(3) a volume of water filling the region between said evaporator tubeand said heat exchange tube; and

(4) passage means for passing any refrigerant leaking from saidevaporator tube into said water to a desired location.

4. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide cooling, saidevaporator comprising:

(1) an evaporator passage including an evaporator tube connected toreceive liquid refrigerant from said condenser and to dischargevaporized refrigerant to said absorber;

(2) a heat exchange tube enclosing at least a portion of said evaporatortube;

(3) a liquid medium filling the region between said evaporator tube andsaid heat exchange tube;

(4) a corrosion inhibitor dissolved in said liquid medium to inhibitcorrosion of said evaporator tube; and

(5) passage means for passing any refrigerant leaking from saidevaporator tube into said liquid medium to a desired location.

5. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

('B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide cooling,saidevaporator comprising:

( 1) an evaporator passage including an evaporator tube connected toreceive liquid refrigerant from said condenser and to dischargevaporized refrigerant to said absorber,

(1) a heat exchange tube enclosing at least a portion of said evaporatortube, said heat exchange tube being spaced from said evaporator tube,

(3) a fluid medium disposed in and substantially filling the spacebetween said evaporator tube and said heat exchange tube,

(4) passage means for passing any-refrigerant leaking into said spacebetween said evaporatortube and said heat exchange tube to a desiredlocation,- and (5) means to pass air to be cooled over the ex teriorsurface of said heat exchange tube so that said air passes in heatexchange relation with refrigerant in said evaporator tube, said airbeing cooled being separated from said refrigerant by the space betweensaid evaporator tube and said heat exchangetube to prevent contaminationof said air in the event of refrigerant leaking through saidevaporatortu'be. 6. An absorption refrigeration system comprising: (A)an absorber for absorbing refrigerant vapor; (B) a generator forconcentrating weak absorbent solution and forming vapor therefrom; (C) acondenser for condensing refrigerant vaporized in said generator; and(D) an evaporator for evaporating a refrigerant to provide cooling, saidevaporator comprising:

(1) a plurality of parallel open ended, heat exchange tubes adapted tobe disposed in a location to have air passed over the exterior surfacesof said heat exchange tubes to cool said air,

(2) an evaporator tube disposed within each of said heat exchange tubes,said evaporator tubes being connected together by passage means to forman evaporator passage,

(3) a liquid medium substantially filling the space between saidevaporator tubes and said heat exchange tubes; and

(4) passage means placing said space filled with said liquid medium incommunication with a desired location for exhausting any refrigerantvapor leaking into said space to said desired location to effectivelyprevent contamination of the air being cooled with refrigerant byventing any refrigerant leaking through said evaporator passage to saiddesired region through said liquid filled space. 7. An absorptionrefrigeration system comprising: (A) an absorber forabsorbingrefrigerant vapor; (B) a generator for concentrating weak absorbentsolution and forming vapor therefrom; (C) a condenser for condensingrefrigerant vaporized in said generator; and (D) an evaporator forevaporating a refrigerant to provide cooling, said evaporatorcomprising:

(1) a heat exchanger including a heat exchange tube having an open end,

(2) an evaporator tube disposed within said heat exchange tube, saidevaporator tube being connected to receive refrigerant from saidcondenser and to discharge vapor formed therein to said (3) liquidheader means disposed about said open end of said heat exchange tube,

(4) a liquid medium disposed in said liquid header means, said liquidmedium filling said header means to a level above said heat exchangetube, and

(5) means to vent said liquid header to a desired location to pass anyrefrigerant which leaks from said evaporator tube to said desiredlocation through said liquid medium and to prevent leakage of saidrefrigerant into air passing over said heat exchange tube.

8. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide cooling, saidevaporator comprising:

( 1) a heat exchanger including a heat exchange tube having an open end,

(2) an evaporator tube disposed within said heat exchange tube, saidevaporator tube being connected to receive refrigerant from said con-'denser and to discharge vapor formed therein to said absorber,

(3) liquid header means disposed about said open end of said heatexchange tube,

- (4) a liquid medium disposed in said liquid header means, said liquidmedium filling said header means to a level above said heat exchangetube,

(5) means to vent said liquid header to a desired location to pass anyrefrigerant which leaks from said evaporator tube to said desiredlocation through said liquid medium and to prevent leakage of saidrefrigerant into air passing over said heat exchange tube, and

(6) a layer of a relatively less volatile and relatively lighter liquidoverlying the surface of said liquid medium to inhibit evaporationthereof.

9. An absorption refrigeration system comprising:

(A) an absonberfor absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide c'oolin-g,said evaporator comprising:

(1) a plurality of heat exchange tubes disposed in parallel relation toeach other, said heat exchange tubes having open e-nds, and beingadapted to have air passed over their exterior surface for cooling saidair,

(2) a pair of liquid headers disposed about the open ends of each ofsaid heat exchange tubes at both ends thereof,

(3) an evaporator tube disposed within said heat exchange tubes, saidevaporator tube being connected to receive refrigerant from saidcondenser and to discharge refrigerant vapor formed therein to saidabsorber,

(4) a liquid heat'exchange medium disposed between said evaporator tubeand said heat exchange tubes, and in said headers, and

(5) passage means for passing refrigerant from said headers to a desiredlocation so as to prevent passage of refrigerant from said evaporatortube into the air being cooled in the event of a leak in said evaporatortube.

10.- An absorption refrigeration. system employing ammonia as arefrigerant and comprising:

, (A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a' refrigerant to provide cooling,said evaporator comprising:

(1) a pair of spaced, tube-sheets,

(2) a plurality of open ended heat exchange tubes extending through saidtube sheets to form a heat exchanger,

(3) a header enclosing the open ends of said heat exchange tubes at eachof said tube sheets, said header forming a chamber adapted to hold aliquid, and both of said headers having an upper region in communicationwith the atmosphere for venting :gas from said header to said ambientatmosphere, said headers being exposed to the ambient atmosphere forheat exchange therewith,

(4) an evaporator passage comprising an evaporator tube disposed withinand in spaced relation with each of said heat exchange tubes, saidevaporator tubes being connected together by return passages to form anevaporator coil, said return passages being disposed within saidheaders, said evaporator coil being connected to receive liquid ammoniafrom said condenser and to discharge ammonia vapor formed therein tosaid absorber,

() Water substantially filling said headers to a level above said heatexchange tubes and the spaces between said heat exchange tubes and saidevaporator tubes, and

(6) a layer of oil covering the surface of said Water in the upperregions of said headers to inhibit evaporation of water from saidheaders into the ambient air.

11. An absonpton refrigeration system comprising: a

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and I (D) an evaporator for evaporating a refrigerant to providecooling, said evaporator comprising:

-(1) an evaporator passage including an evaporator tube connected toreceive liquid refrigerant from said condenser and to dischargevaporized refrigerant to said absorber,

(2) a heat exchange tube enclosing at least a portion of said evaporatortube,

(3) a liquid medium disposed between said evaporator tube and said heatexchange tube,

(4) passage means for passing any refrigerant leaking from saidevaporator tube into said liquid medium to a desired location; and

(5 a layer of a relatively lighter and less volatile liquid covering thesurface of said liquid medium to inhibit evaporation thereof.

12. An absorption refrigeration system comprising:

(A) an absorber for absorbing refrigerant vapor;

(B) a generator for concentrating weak absorbent solution and formingvapor therefrom;

(C) a condenser for condensing refrigerant vaporized in said generator;and

(D) an evaporator for evaporating a refrigerant to provide cooling, saidevaporator comprising:

(1) an evaporator passage, said evaporator passage being connected by arefrigerant liquid passage to receive liquid refrigerant from saidcondenser, and being connected by a refrigerant vapor passage todischarge refrigerant vapor to said absorber,

(2) means to pass air to be cooled "in heat exchange relation with saidevaporator,

(3) said refrigerant liquid and refrigerant vapor passages beingenclosed in an outer tube extending from said evaporator, said outertube being spaced from said refrigerant passages, and

(4) passage means to vent the space between said outer tube and saidrefrigerant passages to a desired location to effectively preventcontamination of air being cooled by said evaporator with refrigerant inthe event of leakage thereof from one of said passages by passing saidrefrigerant through the space between said outer tube and saidrefrigerant passage to said desired location. 13. An absorptionrefrigeration system comprising: (A) an absorber for absorbingrefrigerant vapor; (B) a generator for concentrating weak absorbentsolution and forming vapor therefrom; (C) a condenser for condensingrefrigerant vaporized in said generator; and (D) an evaporator forevaporating a refrigerant to provide cooling, said evaporatorcomprising:

(1) an evaporator passage disposed at a location remote from saidabsorber, condenser and generator, said evaporator passage beingconnected by a refrigerant liquid passage to receive liquid refrigerantfrom said condenser, and being connected by a refrigerant vapor passageto discharge refrigerant vapor to said absorber,

(2) means to pass air to be cooled in heat exchange relation with saidevaporator,

(3) said refrigerant vapor passage and said refrigerant liquid passagebeing disposed in heat exchange relation with each other,

(4) said refrigerant passages being enclosed in an outer tube extendingfrom said evaporator, said outer tube being spaced from the outermost ofsaid refrigerant passages, and

(5) passage means to vent the space between said outer tube and saidrefrigerant passages to a desired location to effectively preventcontamination of air being cooled by said evaporator with refrigerant inthe event of leakage thereof from one of said passages by passing saidrefrigerant through the space between said outer tube and saidrefrigerant passage to said desired location.

References Cited by the Examiner Rhodes 62399 X LLOYD L. KING, PrimaryExaminer.

1. AN ABSORPTION REFRIGERATION SYSTEM COMPRISING: (A) AN ABSORBER FORABSORBING REFRIGERANT VAPOR; (B) A GENERATOR FOR CONCENTRATING WEAKABSORBENT SOLUTION AND FORMING VAPOR THEREFROM; (C) A CONDENSER FORCONDENSING REFRIGERANT VAPORIZED IN SAID GENERATOR; AND (D) ANEVAPORATOR FOR EVAPORATING A REFRIGERANT TO PROVIDE COOLING, SAIDEVAPORATOR COMPRISING: (1) AN EVAPORATOR PASSAGE INCLUDING AN EVAPORATORTUBE CONNECTED TO RECEIVE LIQUID REFRIGERANT FROM SAID CONDENSER AND TODISCHARGE VAPORIZED REFRIGERANT TO SAID ABSORBER; (2) A HEAT EXCHANGETUBE ENCLOSING AT LEAST A PORTION OF SAID EVAPORATOR TUBE; (3) A LIQUIDMEDIUM FILLING THE REGION BETWEEN SAID EVAPORATOR TUBE AND SAID HEATEXCHANGE TUBE; AND (4) A PASSAGE MEANS FOR PASSING ANY REFRIGERANTLEAKING FROM SAID EVAPORATOR TUBE INTO SAID LIQUID MEDIUM TO A DESIREDLOCATION.